What Is It Wednesday – Chain Wear

No, not referring to some haute couture line made up of bicycle parts, which could actually be a hot new trend so don’t steal it in case I want to go into the fashion world one of these days. No, chain wear refers to the overall health of your chain and what many, including up til more recently – ME – refer to as chain stretch.

We’ll look a little bit about the different parts of a  chain so that we  can understand how chains can wear over time. We’ll also see how to measure our chains to see whether it’s time to replace or if we still have a few more miles left. Alright, let’s go!

Story Time

So the VERY first WIIW I did was on bike anatomy. Researching that has helped me out on more than one occasion when troubleshooting a problem that I might have otherwise just brought my bike in to a shop. Don’t get me wrong – I absolutely LOVE supporting my local bike shops, but if it’s simple and I can handle it, then I want to do it myself. So last night as I was riding, my chain popped off and got wedged in between the chain ring and the frame – and it was in there GOOD. When I say GOOD, I mean I had to take a flat head screwdriver and a hammer to tap it out link by link GOOD.

Let’s back up just a little bit – the last time I cleaned, degreased, and lubed my bike I took note that it’s been a long time since I’ve had my bike, and I wondered if the chain was still in good shape. I meant to check it out at that point but it got dark, I got tired, and I forgot. More recently I’ve had my chain pop two or three times, this last one being the worst. Once I got the chain off with aforementioned hammer and screwdriver combo I looked up how to measure my chain. Being the experiential based blogger that I am, I thought there’s gotta be a blog in here somewhere. And voila, there is!

Chain 101

The bike anatomy post I did for the first WIIW is more of a gross anatomy breakdown, now this is zooming in on one very specific part. So, let’s take a look at a couple photos. The first one from Tsubaki shows a couple varieties of chain parts. I thought this would be helpful to see, just in case your chain doesn’t look like mine, no worries. The second photo is what we’re going to be going by for this post.

So the basic parts you should know about: inner plate, outer plate, roller, pin, and bush. The outer and inner plates are pretty much self explanatory – get in real close to your bike chain and you’ll see that the links are held together by an inner plate and then a pair of outer plates sandwich the ends of two links together to form a chain. The teeth of your chain rings slip in the spot formed by the gap between each roller. The roller takes the impact of the chain rings and rolls on and off the teeth as it circumnavigates the chain ring. In fact, the more wear on a chain, the higher the rollers will ride on the teeth, which contributes to the teeth wear. The bush is inside the roller, it absorbs shock and is a load bearing part that the pin fits inside of. The pin, or rivet, holds the whole system together. it passes through the outer and inner plates into the bush which is inside the roller and back out the other inner and outer plates. So needless to say it’s a vital component. The space between pins is referred to as the pitch and should be 0.5″, whereas the distance between each link is 1″.

Chain Wear Not Stretch

So you’ll often hear that a chain stretches over time and on one hand this is true, the length between links can expand, but it’s not like the chain is actually stretching. What happens is that over time the parts of your chain that were so tight fitted become looser and the bush starts to sit to one side instead of in the dead center of the roller and therefore you get a greater distance between pins and links. RJ the Bike Guy has a great video up about this, and in fact his video was one of the ones I used to educate myself on how to measure a chain.

Credit: RJ the Bike Guy

Measuring Your Chain

If you have a chain checker, great! All you have to do is insert one end and drop it in to see if the other end doesn’t just easily slide in. Some chain checkers are double sided for anywhere between 0.5 – 1.0% wear. But fear not, if you don’t have a chain checker as I assume most of us may not, you can simply use a ruler like I did.

Credit: Bike Radar

Go grab your ruler and we’ll work through this step by step. But before we begin, you should know the distance between each link should be 1 in. (2.54 cm.), meaning 6 links should equal 6″, 12 links should be 12″ and so on. Additionally the longer the ruler, the easier it is to see how worn your chain may be as the acceptable loss before you need to replace your chain is roughly 1/16″ over the course of a 12″ length of chain. I am using a shorter ruler because A) it’s what I had available and B) my bike is so compact that getting a 12″ length of straight chain would be incredibly difficult. Since I am using a 6″ ruler, my acceptable difference will be just 1/32″ – basically I need to be SPOT ON.

  1. Locate a good spot on your chain to measure, you want a good run of straight chain. Either the length from the cassette to the chain ring or the chain ring to the rear derailleur will do.
  2. Find your starting point – I prefer to use the left pin that goes through an outer plate. Line up your ruler to the very center of this pin. Make sure you’re lining up with the 0 point on your ruler, not necessarily the ruler edge which might extend past 0.
  3. Align the ruler so that it is parallel with the chain length and running through the middle of each link.
  4. If your chain is new or has little wear, the 12″ tick (or 6″ tick in my case) will line up with the dead center of the pin. If you used the left pin on an outer plate like I did, then you should also end in the same spot at the end of your ruler.
  5. Determine if you need a new chain.

It is a little difficult to see in my photos simply because trying to take an in-focus photo and hold the ruler up to the chain at the same time was a challenge. Off-camera I can say that my chain was certainly about 1/16″ past the 6″ mark, which is equivalent to being 1/8″ past the 12″ mark.

What does all that mean? Well let’s just talk about a 12″ section of chain, since most of you will measure that way. If the center of the pin extends beyond 12″ and is still within 1/16″, then you’re fine, your chain doesn’t need to be replaced yet. If it’s in between 1/16″ and 1/8″ you should replace it so that it doesn’t start to damage the teeth on the chain rings and cassette. Anything longer than 1/8″ REALLY needs to be replaced and likely so do the cassette and chain rings.

Right now, scaling down for my 6″ measurement, I need to replace my chain right away. In theory I should also replace my cassette and chain rings but looking at them, they still look fair, not great, but fair. So I will likely replace the chain this week and then the cassette and chain rings in the near future.

Well I hope that was as informative to you as it was for me. I suspected my chain needed to be replaced but this confirmed it, and it’s a simple way to check. It’s one of those things that now that I am riding my bike regularly I will have to keep an eye on it more diligently.

I hope you’re liking these WIIWs and I have plenty of other ideas in mind for future posts. I had planned an adaptive biking post but I will be holding off on that because I will be sitting down with a adaptive sports organization after our big move and would love to work that into the post. In the meantime, if you have any suggestions, drop me a line, I’d love to read them!